Standard wheelchair designs utilize wheel mounted frames having a seat, a back rest, and opposed arm rests. Side panels are in some cases provided between the seat and the arm rests. Nowadays each side of the frame is generally mounted on a large diameter propulsion wheel located near the rear of the wheelchair and a smaller caster-mounted wheel located near the front of the frame. Hand rims are typically attached near the outer surfaces of the rear propulsion wheels to enable the chair occupant to propel the chair by gripping the hand rims and manually rotating the wheels. However, whether because of convenience or lack of care, the chair occupant will often grip the treads of the propulsion wheel rather than the hand rim. This practice can be unsanitary and even dangerous.
A number of devices have been desfgned to enable a wheelchair occupant to manually propel the propulsion wheels without requiring hand contact with the wheel tread. U.S. Pat. No. 2,876,486 to Lindstrom discloses a flexibly resilient handgrip which serves as a barrier between the wheel tread and the hand of the wheelchair occupant. Such a device requires a manual dexterity often lacking in wheelchair users, and can fall from the occupant's possession if not perpetually anchored within reach. A manual self-propulsion mechanism for wheelchair occupants which comprises axle-mounted levers radially extending from the propulsion wheels and carrying contact shoes for engaging the wheel tread is shown in U.S. Pat. No. 3,189,368 to Petersen. Another axle-mounted, tread-engaging lever drive is shown in U.S. Pat. No. 2,130,426 to Henderson. Side-by-side wheel rims which may be frictionally engaged by sliding contact shoes having knob-like hand grips are shown in U.S. Pat. No. 3,623,748 to Haynes. These four mechanisms might with varying degrees of difficulty be adapted for retrofitting wheelchairs of conventional design. However, the gouging action of the Henderson device can lead to a wheel tread wear, and the other mechanisms suffer the disadvantages of placing a user's hands in close proximity to the wheel treads with a resulting likelihood that contaminating contact or injury to the user's hand will occur. The Haynes device also lacks reverse propulsion capability and thus seriously limits a user's maneuverability.
A sprocketed hand wheel which is connected through a drive chain to a sprocketed forward-mounted propulsion wheel is shown in U.S. Pat. No. 2,847,058 to Lee. Pivotal yolk propulsion levers which are mounted to the propulsion wheel axle are shown in U.S. Pat. No. 3,301,574 to Good, and a lever operated crank-shaped propulsion wheel axle is shown in U.S. Pat. No. 3,666,292 to Bartos. These three devices are shown as components of custom designed wheelchairs and are not generally suitable for more universal use with the common designs of modern wheelchairs. U.S. Pat. No. 4,453,729 to Lucken shows another customized wheelchair having a lever-driven device which provides propulsion wheel drive through axle ratchets. European Pat. No. 0,004,205 to Mitchell shows a customized velociman having two propulsion wheels which are individually propelled by manually operated ratchet drive mechanisms that engage the propulsion wheel shafts. U.S. Pat. No. 3,994,509 to Schaeffer, describes a lever powered clutch drive for wheelchairs having customized propulsion wheels with sprocketed center hubs.
In some designs such as that shown in U.S. Pat. No. 3,104,112 to Crail, crank-driven friction wheels have been provided to directly engage the treads of the wheelchair propulsion wheels. Upon cranking, the friction wheels rotate to in turn drive the propulsion wheels. Motor driven driving drums as shown in U.S. Pat. No. 2,798,565 to Rosenthal, et al. have also been placed in direct contact with wheelchair propulsion wheels to provide frictional propulsion as the drums rotate. Neither of these devices demonstrates the simplicity, efficiency or mechanical advantages of a manually operated bar lever; nor is either device adapted for convenient installation on modern conventional wheelchairs.